what is proper procedure to fill hydrostatic oil in transmission

I am working on a Honda hrc 2163 hxa mower.I had taken the fluid level dip stick to check transmission fluid level and didn't put it back I went to do something else and when I got back

i then started to take the blade clutch out and I tipped the mower on its side and lost a all the transmission oil

my question is what is the proper oil for this transmission and procedure to refill the oil and take out any air bubbles that might be in there

tia